Zooplankton of the frontal zone of the gulf stream(region of the Newfoudland banks slope)

摘要

During the past few years,from 1995 to 2001,the vertical distribution of meso-and macroplakton over the entire water column (0-3700 m) has been studied at the front of the Gulf Stream within a fixed area centered at 41deg44'N,49deg55'W.In order to cover the widest possible size spectrum of plankton,in collecting the materials we used 150-1 bottles,BR 113/140 xlosing planktonnets,Isaacs-Kidd midwater tralws,and visual counting from the mir submersibles.The mesoplankton supplied from the north to the frontal zone,loses its activity and dies out,providing an easy food for macroplanktonic necrophagous predators form the community of the North Atlantic Anticyclonic Gyre.These carnivores ae mainly represented by the pelagic shrimps Acanthephyra,which forms a sort of a live network that eats out the mesoplankton supplied.In so doing,at a depth of 600-1300 m and deeper,their biomassmay exceed the biomass of mesoplankton by a factor of 6-25.Here,the total zooplankton biomass in the layer 0-3000 mmay reach 125-180 g/m~3,which is higher than in the most productive boreal regions of the ocean.Depending on the Gulf Stream meandering,the frontal zone either crossed the site or moved south or north of it.In theyears when the front moved far away from the site,the pattern changed and the number of shrimps decreased significantly.The portion of the frontalzone studied may probably be regarded as a region for comercial fishery of mesopelagic fishes.